Apple's latest OS X update, Mountain Lion, adds a slate of new features, nearly all derived from iOS 5. There's one big omission, however: Siri, Apple's voice-controlled virtual assistant, does not make the migration from mobile to desktop.

Now, technically, Siri isn't a part of iOS 5. It's marketed as the most game-changing feature of the iPhone 4S (which runs iOS 5), and Apple has remained mum on whether Siri will ever be ported to other devices — this to the pique of independent developers who've hacked the feature to run on everything from the iPod touch to thermostats.Clearly, Siri is Apple's most celebrated user feature. And, clearly, there's interest to see it appear on other Apple devices. Indeed, companies throughout the consumer tech industry are exploring novel new user interface models, including voice-control and gesture-control.

But porting Siri to Mountain Lion desktops would pose several challenges. Apple was smart to leave it out of the latest desktop update.